Self-limiting selective etching systems and methods

ABSTRACT

Exemplary etching methods may include flowing a hydrogen-containing precursor into a substrate processing region of a semiconductor processing chamber. The methods may include flowing a fluorine-containing precursor into the substrate processing region. The methods may include contacting a substrate housed in the substrate processing region with the hydrogen-containing precursor and the fluorine-containing precursor. The substrate may define a trench, and a layer of an oxygen-containing material may be disposed within the trench and exposed on the substrate. The methods may include halting delivery of the hydrogen-containing precursor. The methods may also include removing the oxygen-containing material.

TECHNICAL FIELD

The present technology relates to semiconductor processes and equipment. More specifically, the present technology relates to selectively etching oxygen-containing structures.

BACKGROUND

Integrated circuits are made possible by processes which produce intricately patterned material layers on substrate surfaces. Producing patterned material on a substrate requires controlled methods for removal of exposed material. Chemical etching is used for a variety of purposes including transferring a pattern in photoresist into underlying layers, thinning layers, or thinning lateral dimensions of features already present on the surface. Often it is desirable to have an etch process that etches one material faster than another facilitating, for example, a pattern transfer process. Such an etch process is said to be selective to the first material. As a result of the diversity of materials, circuits, and processes, etch processes have been developed with a selectivity towards a variety of materials.

Etch processes may be termed wet or dry based on the materials used in the process. A wet HF etch preferentially removes silicon oxide over other dielectrics and materials. However, wet processes may have difficulty penetrating some constrained trenches and also may sometimes deform the remaining material. Dry etches produced in local plasmas formed within the substrate processing region can penetrate more constrained trenches and exhibit less deformation of delicate remaining structures. However, local plasmas may damage the substrate through the production of electric arcs as they discharge.

Thus, there is a need for improved systems and methods that can be used to produce high quality devices and structures. These and other needs are addressed by the present technology.

SUMMARY

Exemplary etching methods may include flowing a hydrogen-containing precursor into a substrate processing region of a semiconductor processing chamber. The methods may include flowing a fluorine-containing precursor into the substrate processing region. The methods may include contacting a substrate housed in the substrate processing region with the hydrogen-containing precursor and the fluorine-containing precursor. The substrate may define a trench, and a layer of an oxygen-containing material may be disposed within the trench and exposed on the substrate. The methods may include halting delivery of the hydrogen-containing precursor. The methods may also include removing the oxygen-containing material.

In some embodiments, the hydrogen-containing precursor may be maintained fluidly isolated from a plasma formable within the semiconductor processing chamber in a remote plasma region of the semiconductor processing chamber. The hydrogen-containing precursor may be or include water vapor. The fluorine-containing precursor may be or include anhydrous hydrogen fluoride. The substrate may also include an exposed region of hafnium oxide, zirconium oxide, aluminum oxide, or other high-k materials including metal-containing materials. The oxygen-containing material may be selected from the group consisting of silicon dioxide, silicon oxycarbide, silicon oxynitride, or silicon oxycarbonitride.

The etching method may be performed at a temperature below or about 0° C. The etching method may be performed at a temperature above a freezing point of water at operating chamber conditions. The fluorine-containing precursor may be continually flowed subsequent halting the flow of the hydrogen-containing precursor. The fluorine-containing precursor may be flowed at a flow rate below or about 1 slm during the etching method. The fluorine-containing precursor may be pulsed during the etching method. The fluorine-containing precursor may be pulsed off for at least two seconds during each cycle of pulsing performed during the etching method. The substrate processing region may be maintained plasma free during the etching method.

Some embodiments of the present technology may also encompass removal methods, which may include flowing water vapor into a substrate processing region at a temperature below or about 0° C. The methods may include flowing a fluorine-containing precursor into the substrate processing region of a semiconductor processing chamber. The methods may include contacting a substrate housed in the substrate processing region with the water vapor and the fluorine-containing precursor. The substrate may define a trench, and a layer of an oxygen-containing material may be disposed within the trench and exposed on the substrate. The methods may include halting the flow of water vapor while maintaining the flow of the fluorine-containing precursor. The methods may also include removing the oxygen-containing material.

In some embodiments, the water vapor may be delivered into the substrate processing region at a temperature above or about −40° C. The fluorine-containing precursor may be flowed at a rate of less than or about 500 sccm during the removal method. The fluorine-containing precursor may be delivered in pulses. The delivery may be characterized by a first period of time during which the fluorine-containing precursor is flowed, and a second period of time during which the fluorine-containing precursor flow is halted. The first period of time and the second period of time may both be greater than or about 2 seconds. The fluorine-containing precursor may be anhydrous hydrogen fluoride, and the substrate processing region may be maintained plasma-free during the removal method.

Some embodiments of the present technology may also encompass etching methods. The methods may include flowing a hydrogen-containing precursor into a substrate processing region of a semiconductor processing chamber while maintaining the substrate process region at a temperature between about −50° C. and about 0° C. The methods may include flowing anhydrous hydrogen fluoride into the substrate processing region. The methods may include contacting a substrate housed in the substrate processing region with the hydrogen-containing precursor and the anhydrous hydrogen fluoride. The substrate may define a trench, and a layer of an oxygen-containing material may be disposed within the trench and exposed on the substrate. The methods may include halting the flow of the hydrogen-containing precursor. The methods may include removing the oxygen-containing material.

Such technology may provide numerous benefits over conventional systems and techniques. For example, the processes may allow high-aspect-ratio features to be etched without eroding other exposed materials. Additionally, the processes may produce a self-limiting etch, where etching ceases once the desired material has been fully removed. These and other embodiments, along with many of their advantages and features, are described in more detail in conjunction with the below description and attached figures.

BRIEF DESCRIPTION OF THE DRAWINGS

A further understanding of the nature and advantages of the disclosed technology may be realized by reference to the remaining portions of the specification and the drawings.

FIG. 1 shows a top plan view of one embodiment of an exemplary processing system according to embodiments of the present technology.

FIG. 2A shows a schematic cross-sectional view of an exemplary processing chamber according to embodiments of the present technology.

FIG. 2B shows a detailed view of a portion of the processing chamber illustrated in FIG. 2A according to embodiments of the present technology.

FIG. 3 shows a bottom plan view of an exemplary showerhead according to embodiments of the present technology.

FIG. 4 shows exemplary operations in a method according to embodiments of the present technology.

FIGS. 5A-5C show cross-sectional views of substrates being processed according to embodiments of the present technology.

FIGS. 6A-6B show operational effects on etching according to embodiments of the present technology.

Several of the figures are included as schematics. It is to be understood that the figures are for illustrative purposes, and are not to be considered of scale unless specifically stated to be of scale. Additionally, as schematics, the figures are provided to aid comprehension and may not include all aspects or information compared to realistic representations, and may include additional or exaggerated material for illustrative purposes.

In the appended figures, similar components and/or features may have the same reference label. Further, various components of the same type may be distinguished by following the reference label by a letter that distinguishes among the similar components. If only the first reference label is used in the specification, the description is applicable to any one of the similar components having the same first reference label irrespective of the letter.

DETAILED DESCRIPTION

Diluted acids may be used in many different semiconductor processes for cleaning substrates and removing materials from those substrates. For example, diluted hydrofluoric acid can be an effective etchant for silicon oxide, and may be used to remove silicon oxide from silicon surfaces. After the etching or cleaning operation is complete, the acid may be dried from the wafer or substrate surface. Using dilute hydrofluoric acid (“DHF”) may be termed a “wet” etch, and the diluent is often water. Additional etching processes may be used that utilize precursors delivered to the substrate. For example, a plasma species may be delivered to a wafer along with water vapor to form an etchant mixture as well.

Although wet etchants using aqueous solutions or water-based processes may operate effectively for certain substrate structures, the water may pose issues in a variety of conditions. For example, in some oxide etch processes, including silicon dioxide as one non-limiting example, utilizing water, as well as conditions at which the etch process is performed, may create etch processes that may not be well controlled. Again with the non-limiting example of etching silicon dioxide, etchants may include a fluorine-containing precursor as well as a hydrogen-containing precursor. In one example, the fluorine-containing precursor may be anhydrous hydrogen fluoride, and the hydrogen-containing precursor may be water. The chemical process occurring may include the following reaction:

SiO₂+4HF+H₂O→SiF₄+H₂O+2H₂O

As illustrated, along with the formation of volatile silicon tetrafluoride, the etch reaction may produce additional water as well. As hydrogen fluoride continues to be flowed, the etch process may proceed faster due to the increasing amount of water being produced at the etch front to form etchant with the hydrogen fluoride. Although the oxide may be removed, control of the removal may be difficult, and the etch process may essentially create a runaway scenario in which as long as the fluorine-containing precursor is flowed, the etch process will self-sustain and increase in speed. Conventional techniques tend to continue to flow water into the processing chamber, or maintain an amount of relative humidity that delivers even more water, producing a further lack of control on the reaction process.

Utilizing water during etch processes may also pose issues when utilized on substrates including metal materials. For example, certain later fabrication processes, such as producing air gaps, removing oxide dielectric, or other processes to remove oxygen-containing materials, may be performed after an amount of metallization has been formed on a substrate. If water is utilized in some fashion during the etching, an electrolyte may be produced, which when contacting the metal material, may cause galvanic corrosion to occur between dissimilar metals, and the metal may be corroded or displaced in various processes. Although some conventional processes have avoided this issue by utilizing alternative precursors, they may be unsuitable for fabrication processes in which multiple exposed materials are located, which may include silicon oxide, silicon nitride, as well as exposed metal.

Hafnium oxides have become prevalent in many semiconductor structures as well, along with other high-k materials including zirconium oxide, aluminum oxide, and other high-k materials and metal-containing materials, and water may affect hafnium oxide layers formed around features, such as metal gates. Hafnium oxide may be characterized by a more porous structure which may absorb fluorine containing precursors. When water is introduced to these structures, a hydroxide of hafnium may be produced, which may exhibit flowability and swelling, and discreet hafnium oxide structures may be partially or fully displaced or otherwise damaged by these etching methods.

The present technology overcomes these issues by performing a self-limiting and self-catalyzed etch process that allows removal of material through high aspect ratio features, as well as removal of oxide relative to a host of other materials. The processes may or may not utilize plasma effluents as part of the etchant recipes in different embodiments. The technology may be capable of selectively etching oxide-containing materials relative to carbon-containing or nitrogen-containing materials. Additionally, based on the control of the etch process, exposed carbon-containing or nitrogen-containing materials may be protected during the etching of what may conventionally otherwise be lower-selectivity etches. In embodiments in which a plasma may not be formed, formation of oxygen and hydroxyl radicals may be minimized, which may further protect surrounding structures. Finally, by utilizing a minimum amount of water to catalyze oxide removal, the etch chemistry may operate essentially on oxide surfaces alone. This may reduce effects on exposed regions of metal materials including hafnium dioxide, where additional spacer layers may further protect the structure along sidewalls through the substrate. Accordingly, damage and displacement of hafnium and other metal structures may be minimized or substantially prevented. Indeed, aspects of the present technology may passivate hafnium oxide and other materials from etching based on the etchant materials used.

Although the remaining disclosure will routinely identify specific etching processes utilizing the disclosed technology, it will be readily understood that the systems and methods are equally applicable to deposition and cleaning processes as may occur in the described chambers, as well as other etching technology including back-end-of-line air gap formation and other etching that may be performed with a variety of exposed materials that may be maintained or substantially maintained. Accordingly, the technology should not be considered to be so limited as for use with the exemplary etching processes or chambers alone. Moreover, although an exemplary chamber is described to provide foundation for the present technology, it is to be understood that the present technology can be applied to virtually any semiconductor processing chamber that may allow the operations described.

FIG. 1 shows a top plan view of one embodiment of a processing system 100 of deposition, etching, baking, and curing chambers according to embodiments. In the figure, a pair of front opening unified pods (FOUPs) 102 supply substrates of a variety of sizes that are received by robotic arms 104 and placed into a low pressure holding area 106 before being placed into one of the substrate processing chambers 108 a-f, positioned in tandem sections 109 a-c. A second robotic arm 110 may be used to transport the substrate wafers from the holding area 106 to the substrate processing chambers 108 a-f and back. Each substrate processing chamber 108 a-f, can be outfitted to perform a number of substrate processing operations including the dry etch processes described herein in addition to cyclical layer deposition (CLD), atomic layer deposition (ALD), chemical vapor deposition (CVD), physical vapor deposition (PVD), etch, pre-clean, degas, orientation, and other substrate processes.

The substrate processing chambers 108 a-f may include one or more system components for depositing, annealing, curing and/or etching a dielectric film on the substrate wafer. In one configuration, two pairs of the processing chambers, e.g., 108 c-d and 108 e-f, may be used to deposit dielectric material on the substrate, and the third pair of processing chambers, e.g., 108 a-b, may be used to etch the deposited dielectric. In another configuration, all three pairs of chambers, e.g., 108 a-f, may be configured to etch a dielectric film on the substrate. Any one or more of the processes described may be carried out in chamber(s) separated from the fabrication system shown in different embodiments. It will be appreciated that additional configurations of deposition, etching, annealing, and curing chambers for dielectric films are contemplated by system 100.

FIG. 2A shows a cross-sectional view of an exemplary process chamber system 200 with partitioned plasma generation regions within the processing chamber. During film etching, e.g., titanium nitride, tantalum nitride, tungsten, silicon, polysilicon, silicon oxide, silicon nitride, silicon oxynitride, silicon oxycarbide, etc., a process gas may be flowed into the first plasma region 215 through a gas inlet assembly 205. A remote plasma system (RPS) 201 may optionally be included in the system, and may process a first gas which then travels through gas inlet assembly 205. The inlet assembly 205 may include two or more distinct gas supply channels where the second channel (not shown) may bypass the RPS 201, if included.

A cooling plate 203, faceplate 217, ion suppressor 223, showerhead 225, and a substrate support 265, having a substrate 255 disposed thereon, are shown and may each be included according to embodiments. The pedestal 265 may have a heat exchange channel through which a heat exchange fluid flows to control the temperature of the substrate, which may be operated to heat and/or cool the substrate or wafer during processing operations. The wafer support platter of the pedestal 265, which may comprise aluminum, ceramic, or a combination thereof, may also be resistively heated in order to achieve relatively high temperatures, such as from up to or about 100° C. to above or about 1100° C., using an embedded resistive heater element.

The faceplate 217 may be pyramidal, conical, or of another similar structure with a narrow top portion expanding to a wide bottom portion. The faceplate 217 may additionally be flat as shown and include a plurality of through-channels used to distribute process gases. Plasma generating gases and/or plasma excited species, depending on use of the RPS 201, may pass through a plurality of holes, shown in FIG. 2B, in faceplate 217 for a more uniform delivery into the first plasma region 215.

Exemplary configurations may include having the gas inlet assembly 205 open into a gas supply region 258 partitioned from the first plasma region 215 by faceplate 217 so that the gases/species flow through the holes in the faceplate 217 into the first plasma region 215. Structural and operational features may be selected to prevent significant backflow of plasma from the first plasma region 215 back into the supply region 258, gas inlet assembly 205, and fluid supply system 210. The faceplate 217, or a conductive top portion of the chamber, and showerhead 225 are shown with an insulating ring 220 located between the features, which allows an AC potential to be applied to the faceplate 217 relative to showerhead 225 and/or ion suppressor 223. The insulating ring 220 may be positioned between the faceplate 217 and the showerhead 225 and/or ion suppressor 223 enabling a capacitively coupled plasma (CCP) to be formed in the first plasma region. A baffle (not shown) may additionally be located in the first plasma region 215, or otherwise coupled with gas inlet assembly 205, to affect the flow of fluid into the region through gas inlet assembly 205.

The ion suppressor 223 may comprise a plate or other geometry that defines a plurality of apertures throughout the structure that are configured to suppress the migration of ionically-charged species out of the first plasma region 215 while allowing uncharged neutral or radical species to pass through the ion suppressor 223 into an activated gas delivery region between the suppressor and the showerhead. In embodiments, the ion suppressor 223 may comprise a perforated plate with a variety of aperture configurations. These uncharged species may include highly reactive species that are transported with less reactive carrier gas through the apertures. As noted above, the migration of ionic species through the holes may be reduced, and in some instances completely suppressed. Controlling the amount of ionic species passing through the ion suppressor 223 may advantageously provide increased control over the gas mixture brought into contact with the underlying wafer substrate, which in turn may increase control of the deposition and/or etch characteristics of the gas mixture. For example, adjustments in the ion concentration of the gas mixture can significantly alter its etch selectivity, e.g., SiNx:SiOx etch ratios, Si:SiOx etch ratios, etc. In alternative embodiments in which deposition is performed, it can also shift the balance of conformal-to-flowable style depositions for dielectric materials.

The plurality of apertures in the ion suppressor 223 may be configured to control the passage of the activated gas, i.e., the ionic, radical, and/or neutral species, through the ion suppressor 223. For example, the aspect ratio of the holes, or the hole diameter to length, and/or the geometry of the holes may be controlled so that the flow of ionically-charged species in the activated gas passing through the ion suppressor 223 is reduced. The holes in the ion suppressor 223 may include a tapered portion that faces the plasma excitation region 215, and a cylindrical portion that faces the showerhead 225. The cylindrical portion may be shaped and dimensioned to control the flow of ionic species passing to the showerhead 225. An adjustable electrical bias may also be applied to the ion suppressor 223 as an additional means to control the flow of ionic species through the suppressor.

The ion suppressor 223 may function to reduce or eliminate the amount of ionically charged species traveling from the plasma generation region to the substrate. Uncharged neutral and radical species may still pass through the openings in the ion suppressor to react with the substrate. It should be noted that the complete elimination of ionically charged species in the reaction region surrounding the substrate may not be performed in embodiments. In certain instances, ionic species are intended to reach the substrate in order to perform the etch and/or deposition process. In these instances, the ion suppressor may help to control the concentration of ionic species in the reaction region at a level that assists the process.

Showerhead 225 in combination with ion suppressor 223 may allow a plasma present in first plasma region 215 to avoid directly exciting gases in substrate processing region 233, while still allowing excited species to travel from chamber plasma region 215 into substrate processing region 233. In this way, the chamber may be configured to prevent the plasma from contacting a substrate 255 being etched. This may advantageously protect a variety of intricate structures and films patterned on the substrate, which may be damaged, dislocated, or otherwise warped if directly contacted by a generated plasma. Additionally, when plasma is allowed to contact the substrate or approach the substrate level, the rate at which oxide species etch may increase. Accordingly, if an exposed region of material is oxide, this material may be further protected by maintaining the plasma remotely from the substrate.

The processing system may further include a power supply 240 electrically coupled with the processing chamber to provide electric power to the faceplate 217, ion suppressor 223, showerhead 225, and/or pedestal 265 to generate a plasma in the first plasma region 215 or processing region 233. The power supply may be configured to deliver an adjustable amount of power to the chamber depending on the process performed. Such a configuration may allow for a tunable plasma to be used in the processes being performed. Unlike a remote plasma unit, which is often presented with on or off functionality, a tunable plasma may be configured to deliver a specific amount of power to the plasma region 215. This in turn may allow development of particular plasma characteristics such that precursors may be dissociated in specific ways to enhance the etching profiles produced by these precursors.

A plasma may be ignited either in chamber plasma region 215 above showerhead 225 or substrate processing region 233 below showerhead 225. Plasma may be present in chamber plasma region 215 to produce the radical precursors from an inflow of, for example, a fluorine-containing precursor or other precursor. An AC voltage typically in the radio frequency (RF) range may be applied between the conductive top portion of the processing chamber, such as faceplate 217, and showerhead 225 and/or ion suppressor 223 to ignite a plasma in chamber plasma region 215 during deposition. An RF power supply may generate a high RF frequency of 13.56 MHz but may also generate other frequencies alone or in combination with the 13.56 MHz frequency.

FIG. 2B shows a detailed view 253 of the features affecting the processing gas distribution through faceplate 217. As shown in FIGS. 2A and 2B, faceplate 217, cooling plate 203, and gas inlet assembly 205 intersect to define a gas supply region 258 into which process gases may be delivered from gas inlet 205. The gases may fill the gas supply region 258 and flow to first plasma region 215 through apertures 259 in faceplate 217. The apertures 259 may be configured to direct flow in a substantially unidirectional manner such that process gases may flow into processing region 233, but may be partially or fully prevented from backflow into the gas supply region 258 after traversing the faceplate 217.

The gas distribution assemblies such as showerhead 225 for use in the processing chamber section 200 may be referred to as dual channel showerheads (DCSH) and are additionally detailed in the embodiments described in FIG. 3. The dual channel showerhead may provide for etching processes that allow for separation of etchants outside of the processing region 233 to provide limited interaction with chamber components and each other prior to being delivered into the processing region.

The showerhead 225 may comprise an upper plate 214 and a lower plate 216. The plates may be coupled with one another to define a volume 218 between the plates. The coupling of the plates may be so as to provide first fluid channels 219 through the upper and lower plates, and second fluid channels 221 through the lower plate 216. The formed channels may be configured to provide fluid access from the volume 218 through the lower plate 216 via second fluid channels 221 alone, and the first fluid channels 219 may be fluidly isolated from the volume 218 between the plates and the second fluid channels 221. The volume 218 may be fluidly accessible through a side of the gas distribution assembly 225.

FIG. 3 is a bottom view of a showerhead 325 for use with a processing chamber according to embodiments. Showerhead 325 may correspond with the showerhead 225 shown in FIG. 2A. Through-holes 365, which show a view of first fluid channels 219, may have a plurality of shapes and configurations in order to control and affect the flow of precursors through the showerhead 225. Small holes 375, which show a view of second fluid channels 221, may be distributed substantially evenly over the surface of the showerhead, even amongst the through-holes 365, and may help to provide more even mixing of the precursors as they exit the showerhead than other configurations.

The chamber discussed previously may be used in performing exemplary methods including etching methods. Turning to FIG. 4 is shown exemplary operations in a method 400 according to embodiments of the present technology. Method 400 may include one or more operations prior to the initiation of the method, including front end processing, deposition, gate formation, etching, polishing, cleaning, or any other operations that may be performed prior to the described operations. The method may include a number of optional operations, which may or may not be specifically associated with some embodiments of methods according to the present technology. For example, many of the operations are described in order to provide a broader scope of the structural formation, but are not critical to the technology, or may be performed by alternative methodology as will be discussed further below. Method 400 describes operations shown schematically in FIGS. 5A-5C, the illustrations of which will be described in conjunction with the operations of method 400. It is to be understood that FIG. 5 illustrates only partial schematic views, and a substrate may contain any number of structural sections having aspects as illustrated in the figures, as well as alternative structural aspects that may still benefit from operations of the present technology

Method 400 may or may not involve optional operations to develop the semiconductor structure to a particular fabrication operation. It is to be understood that method 400 may be performed on any number of semiconductor structures, and FIG. 5 illustrates one exemplary structure of a gate about which an oxide removal operation may be performed. As illustrated in FIG. 5A, the semiconductor structure may represent a device in which a trench, via, or other recessed feature has been formed in a substrate 501. As illustrated, structure 500 may include a substrate 501 made of or containing silicon or some other semiconductor substrate material as well as interlayer dielectric materials through which a recess, trench, via, or isolation structure may be formed. Trench 503, which may also be a via or other recess that is similarly encompassed by the present technology, may include a spacer 505 structure formed between a sidewall 502 of substrate 501 and a material 504 formed or positioned within trench 503. Material 504 may be a metal material such as a gate, a dielectric material, a contact material, a transistor material, or any other material that may be used in semiconductor processes.

It is to be understood that the figure is merely indicative of one of many structures for which the present technology may be applicable. Other exemplary structures may include two-dimensional and three-dimensional structures common in semiconductor manufacturing, and within which an oxide material is to be removed relative to one or more other materials, as the present technology may selectively remove many oxide containing materials, such as silicon oxide, relative to materials having a reduced oxygen content, such as silicon, silicon nitride, and any of the other materials discussed elsewhere. Additionally, although a high-aspect-ratio structure is illustrated and discussed, the technology may be equally applicable to lower aspect ratios and any other structures. Returning to the figure, gate metals and materials may include a number of metal and/or metal-containing species including tungsten, titanium, tantalum, cobalt, aluminum, or any other work-function metal or material which may be incorporated within the structure. About gate or material 504 may be a liner 510 as well as a layer of hafnium oxide 512, which may operate as an additional gate insulator, for example.

Spacer 505 may include a number of layers formed laterally adjacent one another. For example, as illustrated in the figure, spacer 505 may include a first layer 506, and a second layer 508. In some alternative embodiments, second layer 508 may be a different sacrificial layer, or a portion of an interlayer dielectric to be removed. The spacer 505 may include any number of layers in different embodiments, although in some embodiments the spacer may include at least two layers of materials. Some methods of forming an airgap, such as in some embodiments of the present technology, may include forming a sacrificial layer between other layers of the spacer. During subsequent removal, the sacrificial layer may be removed to provide the airgap between the maintained layers of the spacer. In some embodiments, second layer 508 of spacer 505 may illustrate a sacrificial material to be removed from the substrate to produce an airgap between the first layer 506 and a third layer of the spacer 505, not shown.

In some embodiments, although not illustrated, first layer 506 of spacer 505 and second layer 508 of spacer 505 may extend beneath a third layer by some amount as would be understood by one of skill for a finFET structure in which the spacer materials may extend about a fin and source/drain structure formed perpendicular to the illustrated gate. As these layers may be formed over one another during fabrication, the last layer formed, such as a third layer laterally out from second layer 508 may be seated or disposed over the other layers of the spacer 505. In some embodiments, a lateral portion of the sacrificial spacer material may be removed during a self-catalyzing etching operation as will be discussed further below.

It is to be understood that the illustration includes only a schematic view of a spacer according to some embodiments of the present technology, and is not drawn to any particular scale, but is instead illustrated to emphasize certain characteristics of possible structures encompassed by the present technology having an oxide material to be removed. For example, in some embodiments each layer may be formed to a similar thickness laterally, or any individual layer may be thicker than any other layer, or may not be included. Similarly, additional layers of material may be included in a variety of configurations as well. Layers of material according to the present technology may be characterized by any aspect ratios or the height-to-width ratio of the structure, although in some embodiments the materials may be characterized by larger aspect ratios, which may not allow sufficient etching utilizing conventional technology or methodology. For example, in some embodiments the aspect ratio of any layer of an exemplary structure may be greater than or about 10:1, greater than or about 20:1, greater than or about 30:1, greater than or about 40:1, greater than or about 50:1, or greater. Additionally, each layer of spacer 505 may be characterized by a reduced width less than or about 10 nm, less than or about 8 nm, less than or about 6 nm, less than or about 5 nm, less than or about 4 nm, less than or about 3 nm, less than or about 2 nm, less than or about 1 nm, or less, including any fraction of any of the stated numbers, such as 2.5 nm, 1.5 nm, etc. This combination of high aspect ratios and minimal widths may frustrate many conventional etching operations, or require substantially longer etch times to remove a layer, such as layer 508, along a vertical distance through a confined width. Moreover, damage to or removal of other exposed layers may occur with conventional technologies as well.

The materials encompassed by the present technology may include a variety of materials, such as silicon-containing materials, for each of the spacer layers. As previously discussed, substrate 501 may include materials including silicon or polysilicon, silicon germanium, or other materials, including silicon oxide or other dielectric materials when the structure represents material formed overlying a substrate, such as an interlayer dielectric, for example. Although not illustrated, one or more capping materials may be formed over the exposed upper surface of substrate 501 or material 504, and may include oxide and/or nitride materials, or any of the other materials noted here. Spacer 505 may be characterized by multiple layers, each layer of which may be any number of materials. For example, any of the layers may be or include silicon oxide, silicon oxycarbide, silicon oxycarbonitride, silicon carbon nitride, or silicon nitride. In some embodiments adjacent layers of spacer 505 may be different materials. For example, second spacer layer 508 may be a different material from first spacer layer 506.

In some embodiments, first spacer layer 506 may be or include a carbon-containing and/or nitrogen-containing material, such as any of the nitride-containing materials noted above, and second spacer layer 508 may be or include an oxygen-containing material, such as any of the oxygen-containing materials noted above. For example, one possible combination of materials may include silicon carbon nitride for the first spacer layer 506, and silicon oxide, silicon oxycarbide, or silicon oxycarbonitride as the second spacer layer 508. Put another way, in some embodiments, second spacer layer 508 may include a higher oxygen concentration, or a lower carbon concentration, or a lower nitrogen concentration, than first spacer layer 506. As will be explained below, such configurations may advantageously allow selective removal of the second spacer layer 508, while substantially or essentially maintaining the first spacer layer and any number of exposed gate or other metal materials of the substrate.

The method 400 may be performed to remove second spacer layer 508 in embodiments, although any number of oxide or oxygen-containing materials may be removed in any number of structures in embodiments of the present technology. The method may include flowing a hydrogen-containing precursor into the substrate processing region of a semiconductor processing chamber housing the described substrate, or some other substrate, at operation 405. Method 400 may further include flowing a fluorine-containing precursor into the substrate processing region at operation 410. The fluorine-containing precursor may be flowed through a remote plasma region of the processing chamber, such as region 215 described above, although in some embodiments method 400 may not utilize plasma effluents. For example, method 400 may flow a fluorine-containing or other halogen-containing precursor to the substrate without exposing the precursor to a plasma.

The hydrogen-containing precursor may be flowed into the processing region prior to the fluorine-containing precursor, although in some embodiments the precursors may be co-flowed, and the two precursors may be flowed through different or similar portions of the processing chamber. For example, both precursors may be flowed through an entrance to the chamber, or the fluorine-containing precursor may be flowed through a first access to the chamber, and the hydrogen-containing precursor may be flowed through a second access to the chamber. At operation 415, the hydrogen-containing precursor and the fluorine-containing precursor may contact a semiconductor substrate including an oxygen-containing material, such as is illustrated in FIG. 5. The flow of the hydrogen-containing precursor may be halted at operation 420, which will be described further below, and may limit a runaway effect in the etching process, allowing a self-limiting etch process to occur. At operation 425 at least a portion of the second spacer 508, which may be or include an oxygen-containing material, may be removed while maintaining additional layers of spacer 505, such as first layer 506, as well as additionally exposed metals or metal-containing materials, which may include any of the previously noted materials.

Precursors used in the method may include a fluorine-containing precursor or a halogen-containing precursor. An exemplary fluorine-containing precursor may be nitrogen trifluoride (NF₃), which may be flowed into the remote plasma region, which may be separate from, but fluidly coupled with, the processing region. Other sources of fluorine may be used in conjunction with or as replacements for the nitrogen trifluoride. In general, a fluorine-containing precursor may be flowed into the remote plasma region and the fluorine-containing precursor may include at least one precursor selected from the group of atomic fluorine, diatomic fluorine, nitrogen trifluoride, carbon tetrafluoride, hydrogen fluoride including anhydrous hydrogen fluoride, xenon difluoride, and various other fluorine-containing precursors used or useful in semiconductor processing. The precursors may also include any number of carrier gases, which may include nitrogen, helium, argon, or other noble, inert, or useful precursors. Although a plasma may be formed in the process, in some embodiments the fluorine-containing precursor may not be plasma enhanced or radicalized prior to being delivered to the substrate processing region, and in some embodiments no plasma may be formed in exemplary processes. For example, a fluorine-containing precursor, such as anhydrous hydrogen fluoride or any other precursor, may be flowed into the semiconductor processing region without being plasma enhanced prior to contacting the substrate.

The hydrogen-containing precursor may include hydrogen, a hydrocarbon, water vapor, an alcohol, such as isopropyl alcohol, hydrogen peroxide, or other materials that may include hydrogen or a hydroxy moiety as would be understood by the skilled artisan. Additional precursors such as carrier gases or inert materials may be included with the hydrogen-containing precursors as well. In some embodiments, the hydrogen-containing precursor, such as water vapor, may be maintained fluidly isolated from a plasma that may be formed within the remote plasma region. In some embodiments, no plasma may be formed during the etching methods to aid in protecting carbon-containing or nitrogen-containing materials, such as the spacer layers surrounding the sacrificial layer. Although selectivity of a plasma process may etch oxide materials faster than nitride materials, because of the high aspect ratios and relatively thin material widths described above, exposure of sidewalls of first spacer layer 506 to an etchant including water vapor or a hydroxy-containing material may cause thinning to occur during the removal, which may not maintain sufficient thickness of the spacer layer, and may produce adverse effects on exposed metal materials as previously described. In embodiments, the plasma processing region may be maintained plasma free during the removal operations. By plasma free is meant that plasma may not be actively formed within the processing region during the operations, although plasma effluents produced remotely as described earlier, may be used during the operations.

The process of method 400 may include timing aspects as well as temperature and pressure considerations providing an etchant that may be limited in volume at initiation. For example, although a variety of hydrogen-containing or hydroxy-containing materials may be used, in some embodiments water may be flowed into the processing chamber, and may be flowed in a vapor form. The processing chamber may be operated at a temperature and pressure configured to condense a minimum amount of liquid water across a top surface of the substrate including a top surface of each of the spacer layers, which may be exposed. The water provided may be halted after a sufficient amount of water has been produced on the exposed surface of the oxide materials. Advantageously, halting the flow of water may also reduce the development of hexafluorosilicic acid where silicon tetrafluoride may be further developed with additional water and fluorine-containing precursor. This acid may stain and otherwise damage structures, yet when the amount of water is limited according to the present technology, development of the acid may be limited.

As the fluorine-containing precursor is delivered, an etch process may be performed according to the reaction described above. Although other layers may have an exposed surface that causes slight etching to occur, such as for a few monolayers, because the water flow has been stopped, as long as the exposed material is not naturally etched by the fluorine-containing precursor by itself, no further etching may occur. Conversely, because etching of the oxide may produce additional water, the oxide material may continue to etch. As this water is formed substantially or only at the etch front, the etch process may be essentially limited to the oxide material. As illustrated in FIG. 5B, self-generating water layer 515 may be formed across only the exposed oxide surface at the etch front where additional water is produced. Although the fluorine-containing precursor flow may be continued, because other exposed surfaces may not be exposed to additional water, less a discreet amount from initiation desorbed from surfaces as the oxide etch process continues, these materials may be substantially maintained, and may not be etched at all in some embodiments after the initial water delivered has been consumed. The fluorine-containing precursor may then continue the oxide etch reaction producing additional water to maintain etching at the exposed oxide surface, and as illustrated the oxide material may be continually removed with only a continued flow of the fluorine-containing precursor into the chamber.

To produce the etchant according to some embodiments, the hydrogen-containing precursor may be flowed in an initial pulse or burst to initiate the process, and in some embodiments no additional hydrogen-containing precursor may be delivered to the processing chamber. The hydrogen-containing precursor, such as water or any of the previously noted materials may be co-flowed with the delivery of the fluorine-containing precursor, or the hydrogen-containing precursor may be delivered prior to flowing the fluorine-containing precursor. For example, the hydrogen-containing material may be flowed for at least about 2 seconds prior to halting the flow of the hydrogen-containing precursor. Because a temperature gradient may form in certain chambers, such as where sidewalls may be warmer than a central region, in some embodiments the hydrogen-containing precursor may be flowed for greater than or about 3 seconds, greater than or about 4 seconds, greater than or about 5 seconds, greater than or about 6 seconds, greater than or about 7 seconds, greater than or about 8 seconds, greater than or about 9 seconds, greater than or about 10 seconds, greater than or about 20 seconds, greater than or about 30 seconds, greater than or about 45 seconds, greater than or about 1 minute, or more. To limit the amount of condensation formation on exposed surfaces, which may affect the rate of etching as well as the amount of etching of other exposed materials, in some embodiments the first period of time during which only the hydrogen-containing precursor may be flowed may be less than or about 1 minute, and may be less than or about 45 seconds, less than or about 30 seconds, less than or about 20 seconds, less than or about 10 seconds, or less.

The fluorine-containing precursor may be introduced subsequent the delivery of the hydrogen-containing precursor, although in some embodiments the precursors may be co-flowed. The fluorine-containing precursor may be flowed for a period of time to maintain the reaction, and may be continually flowed until all oxide material has been removed, or until a desired amount of the oxide material has been removed. As will be explained further below, delivery of the fluorine-containing precursor may be utilized to tune the etch process to ensure a more linear process, which may be less susceptible to runaway conditions. Accordingly, in addition to controlling the flow rate of the fluorine-containing precursor, the fluorine-containing precursor may be delivered at intervals in a pulsed delivery of material. Accordingly, the fluorine-containing precursor may be delivered for any amount of time to continue an oxide etch process, or the fluorine-containing precursor may be pulsed on for a first period of time, and may be pulsed off for a second period of time during which the flow of the fluorine-containing precursor is halted.

In some embodiments the pulse on period and the pulse off period may be a similar amount of time, although in some embodiments the times may differ, and either the pulse on period or the pulse off period may be longer. Because the etch process may be limited to oxide or oxygen-containing materials once catalyzed, in some embodiments, either with pulsed or continuous flow of the fluorine-containing precursor, the etch process may continue until all oxide material has been removed as illustrated in FIG. 5C. The etch process may naturally cease at this point, as no further water generation may occur at the etch front. Alternatively, after a desired amount of material has been removed, the flow or pulsing of fluorine-containing precursor may be halted, which may cause the etch process to cease.

Process conditions may also impact the operations performed in method 400 as well as other removal methods according to the present technology, and may afford a more controlled self-generating reaction. As previously explained, aspects of the present etch technology relate to utilizing a self-catalyzing and self-sustaining reaction in which additional water may be produced during the etch process to facilitate continued etching. However, because the amount of water may continue to increase as the reaction proceeds, a runaway reaction may occur in which sufficient water is produced to begin attacking other structures. In this scenario, water may begin to pool across the surface of the substrate after sufficient generation, which may lead to corrosion and etching of other structures. Conversely, when properly controlled, the amount of water may be contained as illustrated with etch front fluid or water layer 515, where the water generation is generally contained within the feature being etched. Hence, by maintaining a more linear or tailing etch rate, the etch process may be limited to the oxide features.

Turning to FIG. 6A is shown a chart illustrating the effect of temperature on oxide etch amount for some embodiments of the present technology. Because the etch reaction may proceed based on water retention at the surface of the oxide material, lower temperatures may facilitate maintenance and adsorption of generated water at the surface of the feature to be etched. Line 605 illustrates an etch rate where the temperature may be maintained at 0° C. or above. As illustrated, after an initial amount of etching occurs, the etch process halts completely and no further etching occurs. This may be due to the generated water desorbing from the oxide surface. Thus, despite continued delivery of a fluorine-containing precursor, without water present no further etching may occur. Accordingly, in some embodiments the temperature may be maintained below or about 0° C., and the substrate, pedestal, or chamber temperature during the method 400 may be maintained below or about −2° C., below or about −4° C., below or about −6° C., below or about −8° C., below or about −10° C., below or about −15° C., below or about −20° C., below or about −25° C., below or about −30° C., below or about −40° C., below or about −50° C., or lower. The temperature may also be maintained at any temperature within these ranges, within smaller ranges encompassed by these ranges, or between any of these ranges.

Line 610 illustrates an effect as temperature continues to be reduced. The lower the temperature, the more water may be retained at the surface of the oxide layer, and the more likely a runaway etch process may occur as illustrated by the line. As time proceeds, water is continually generated at a higher rate, and thus the etch rate begins to slope and curve upward. Beyond the edge of the chart, etch rate will continue to escalate, which may cause fluid to pool in a runaway reaction, which may damage other exposed structures. This may occur more so in exemplary processes where the water is allowed to freeze, which may further increase the amount of water retained at the surface, and thus in some embodiments the temperature may be maintained above the freezing point of water at the operating chamber conditions. Accordingly, in some embodiments the temperature may be maintained above or about −100° C. during the etch process, and may be maintained above or about −90° C., above or about −80° C., above or about −70° C., above or about −60° C., above or about −50° C., above or about −40° C., above or about −30° C., above or about −20° C., or higher, as well as within any smaller range incorporated within any of these ranges, as well as within any ranges encompassed by end points defined by and of these stated temperatures with a stated temperature in the ranges above.

Consequently, maintaining the temperate in a range to allow partial retention of water on the surface, while permitting an amount of desorption, may produce a line similar to line 615. As illustrated, the etch process actually plateaus over time, which illustrates that the process is more controlled, and may eventually quench due to full desorption of produced water. By increasing the temperature slightly, a linear etch profile may be produced by which a controlled reaction limited to the oxide material may be maintained.

The pressure within the chamber may also affect the operations performed as well as affect at what temperature the hydrogen-containing precursor may freeze or maintain a particular amount of desorption, and in embodiments the chamber pressure may be maintained below about 500 Torr, below about 400 Torr, below about 300 Torr, below about 200 Torr, below about 100 Torr, below about 50 Torr, below or about 40 Torr, below or about 30 Torr, below or about 25 Torr, below or about 20 Tor below or about 15 Torr, below or about 10 Torr, below or about 9 Torr, below or about 8 Torr, below or about 7 Torr, below or about 6 Torr, below or about 5 Torr, below or about 4 Torr, below or about 3 Torr, below or about 2 Torr, below or about 1 Torr, or less. The pressure may also be maintained at any pressure within these ranges, within smaller ranges encompassed by these ranges, or between any of these ranges. By performing the operations at pressures below about 30 Torr, the selectivity of the process with respect to a carbon-containing or nitrogen-containing material may be increased. Additionally, pressure may influence the freezing point of water and the desorption rate of water developed at the surface, and thus controlling pressure may further control the etch reaction.

Some embodiments of the present technology involve providing an initial amount of water to initiate a reaction in which additional water is generated. Because the water flow is halted, the water flow may not be available to further tune the etch process. However, as the fluorine-containing precursor is flowed, the rate and timing may be controlled to improve control of the etch process being performed. FIG. 6B illustrates the effect of the fluorine-containing precursor flow rate on the linearity of the etch process, and may illustrate the rate for exemplary precursor anhydrous hydrogen fluoride. Line 620 illustrates a flow rate that may cause runaway etching, which may increase development of water that may damage other surfaces. Line 625 shows the effect as the flow rate of the fluorine-containing precursor is reduced, providing a more linear etch process, which may limit formation of water to the oxide material being etched.

Accordingly, the flow rate of the fluorine-containing precursor may be tuned, including in situ, to control the etch process. For example, a flow rate of the fluorine-containing precursor may be reduced, maintained, or increased during the removal operations. During any of the operations of method 400, the flow rate of the fluorine-containing precursor may be between about 5 sccm and about 1,000 sccm. Additionally, the flow rate of the fluorine-containing precursor may be maintained below or about 900 sccm, below or about 800 sccm, below or about 700 sccm, below or about 600 sccm, below or about 500 sccm, below or about 400 sccm, below or about 300 sccm, below or about 200 sccm, below or about 100 sccm, or less. The flow rate may also be between any of these stated flow rates, or within smaller ranges encompassed by any of these numbers.

Adding further control to the etch front and water development, the fluorine-containing precursor may be pulsed in some embodiments, and may be delivered throughout the etch process either continually or in a series of pulses, which may be consistent or varying over time. The pulsed delivery may be characterized by a first period of time during which the fluorine-containing precursor is flowed, and a second period of time during which the fluorine-containing precursor is paused or halted. The time periods may be similar or different from one another with either time period being longer. In embodiments either period of time may be greater than or about 1 second, and may be greater than or about 2 seconds, greater than or about 3 seconds, greater than or about 4 seconds, greater than or about 5 seconds, greater than or about 6 seconds, greater than or about 7 seconds, greater than or about 8 seconds, greater than or about 9 seconds, greater than or about 10 seconds, greater than or about 11 seconds, greater than or about 12 seconds, greater than or about 13 seconds, greater than or about 14 seconds, greater than or about 15 seconds, greater than or about 20 seconds, greater than or about 30 seconds, greater than or about 45 seconds, greater than or about 60 seconds, or longer. The times may also be any smaller range encompassed by any of these ranges.

The hydrogen-containing precursor may be flowed at any of these flow rates depending on the precursor used, which may be any number of hydrogen-containing precursors. For example, in embodiments in which water vapor is utilized, the vapor may be introduced at a rate of at least or about 0.1 g/min until sufficient water has been introduced, which may be less than one minute of time. The water vapor may also be introduced at a rate of at least or about 0.2 g/min, at least or about 0.3 g/min, at least or about 0.4 g/min, at least or about 0.5 g/min, at least or about 0.6 g/min, at least or about 0.7 g/min, at least or about 0.8 g/min, at least or about 0.9 g/min, at least or about 1 g/min, at least or about 1.5 g/min, or more, although the vapor may be introduced below about 5 g/min or below or about 1 g/min to reduce or limit condensation and/or freezing on other components of the chamber and the substrate. The water vapor may also be introduced at a flow rate between any of these stated flow rates, or within smaller ranges encompassed by any of these numbers before being halted.

Second layer 508 of the spacer may be fully removed or partially removed, as previously discussed, while substantially or essentially maintaining first spacer layer 506. Although partial rounding at top portions of spacer layer 506 may occur depending on the materials forming each layer of the spacer 505, minimal removal of spacer layer 506 may occur, as well as removal of any of the other exposed layers including metal-containing layers, and the layers may be more than 50% maintained from an initial formation amount. In some embodiments the other layers may be more than 60% maintained from an initial formation amount, more than 70% maintained from an initial formation amount, more than 80% maintained from an initial formation amount, more than 90% maintained from an initial formation amount, more than 95% maintained from an initial formation amount, more than 97% maintained from an initial formation amount, more than 99% maintained from an initial formation amount, or more.

Because water may be generated to sustain the reaction only as long as additional silicon oxide or other oxide material is present, processes according to the present technology may also be self-limiting. Once the oxide material has been removed, no further water generation may occur, and the process may cease. Additionally, because the water may be limited to the oxide material once the initial injection of water has been consumed or dissipated from other surfaces, the present technology may afford high selectivity and protection of other exposed materials. The present technology may selectively etch silicon oxide, silicon oxycarbide, silicon oxycarbonitride, or other oxygen-containing materials relative to other materials, and may selectively etch some types of silicon oxide relative to other types of silicon oxide. For example, the present technology may etch deposited silicon oxides relative to thermal oxide at a rate of at least about 10:1, and may etch deposited oxides relative to thermal oxide at a rate of at least about 15:1, at least about 20:1, at least about 50:1, at least about 100:1, or more. Deposited oxides may include spin on dielectrics, or deposition techniques including CVD, PECVD, and other deposition techniques. The present technology may also etch any of the oxygen-containing materials relative to silicon nitride, silicon carbon nitride films having any ratio of carbon and nitrogen, or silicon oxycarbonitride, at a rate of at least about 20:1, at least about 25:1, at least about 30:1, at least about 50:1, at least about 100:1, at least about 150:1, at least about 200:1, at least about 250:1, at least about 300:1, at least about 350:1, at least about 400:1, at least about 450:1, at least about 500:1, or more. The processes described may similarly etch the oxygen-containing materials relative to any of the metal or metal-containing materials previously described, and may produce any of the selectivities as noted above with respect to these additional materials.

The previously discussed methods may allow the removal of oxide material from a substrate, which may be from high-aspect-ratio features, while maintaining other materials including metal and metal-containing materials, and other silicon-containing materials. By utilizing the present methods and operations, high-aspect-ratio features having relatively thin widths of initial exposure may be etched while not causing pattern collapse, unlike wet etching, and while not removing or while substantially maintaining other exposed material layers, unlike some conventional dry etching.

In the preceding description, for the purposes of explanation, numerous details have been set forth in order to provide an understanding of various embodiments of the present technology. It will be apparent to one skilled in the art, however, that certain embodiments may be practiced without some of these details, or with additional details.

Having disclosed several embodiments, it will be recognized by those of skill in the art that various modifications, alternative constructions, and equivalents may be used without departing from the spirit of the embodiments. Additionally, a number of well-known processes and elements have not been described in order to avoid unnecessarily obscuring the present technology. Accordingly, the above description should not be taken as limiting the scope of the technology. Additionally, methods or processes may be described as sequential or in steps, but it is to be understood that the operations may be performed concurrently, or in different orders than listed.

Where a range of values is provided, it is understood that each intervening value, to the smallest fraction of the unit of the lower limit, unless the context clearly dictates otherwise, between the upper and lower limits of that range is also specifically disclosed. Any narrower range between any stated values or unstated intervening values in a stated range and any other stated or intervening value in that stated range is encompassed. The upper and lower limits of those smaller ranges may independently be included or excluded in the range, and each range where either, neither, or both limits are included in the smaller ranges is also encompassed within the technology, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included.

As used herein and in the appended claims, the singular forms “a”, “an”, and “the” include plural references unless the context clearly dictates otherwise. Thus, for example, reference to “a precursor” includes a plurality of such precursors, and reference to “the layer” includes reference to one or more layers and equivalents thereof known to those skilled in the art, and so forth.

Also, the words “comprise(s)”, “comprising”, “contain(s)”, “containing”, “include(s)”, and “including”, when used in this specification and in the following claims, are intended to specify the presence of stated features, integers, components, or operations, but they do not preclude the presence or addition of one or more other features, integers, components, operations, acts, or groups. 

1. An etching method comprising: flowing a hydrogen-containing precursor into a substrate processing region of a semiconductor processing chamber; flowing a fluorine-containing precursor into the substrate processing region; contacting a substrate housed in the substrate processing region with the hydrogen-containing precursor and the fluorine-containing precursor, wherein the substrate defines a trench, wherein a layer of an oxygen-containing material is disposed within the trench and exposed on the substrate; halting delivery of the hydrogen-containing precursor; and removing the oxygen-containing material.
 2. The etching method of claim 1, wherein the hydrogen-containing precursor is maintained fluidly isolated from a plasma formable within the semiconductor processing chamber in a remote plasma region of the semiconductor processing chamber.
 3. The etching method of claim 1, wherein the hydrogen-containing precursor comprises water vapor.
 4. The etching method of claim 1, wherein the fluorine-containing precursor comprises anhydrous hydrogen fluoride.
 5. The etching method of claim 1, wherein the substrate further comprises an exposed region of hafnium oxide, zirconium oxide, or aluminum oxide.
 6. The etching method of claim 1, wherein the oxygen-containing material is selected from the group consisting of silicon dioxide, silicon oxycarbide, silicon oxynitride, and silicon oxycarbonitride.
 7. The etching method of claim 1, wherein the etching method is performed at a temperature below or about 0° C.
 8. The etching method of claim 7, wherein the etching method is performed at a temperature above a freezing point of water at operating chamber conditions.
 9. The etching method claim 1, wherein the fluorine-containing precursor is continually flowed subsequent halting the flow of the hydrogen-containing precursor.
 10. The etching method of claim 1, wherein the fluorine-containing precursor is flowed at a flow rate below or about 1 slm during the etching method.
 11. The etching method of claim 10, wherein the fluorine-containing precursor is pulsed during the etching method.
 12. The etching method of claim 11, wherein the fluorine-containing precursor is pulsed off for at least two seconds during each cycle of pulsing performed during the etching method.
 13. The etching method of claim 1, wherein the substrate processing region is maintained plasma free during the etching method.
 14. A removal method comprising: flowing water vapor into a substrate processing region at a temperature below or about 0° C.; flowing a fluorine-containing precursor into the substrate processing region of a semiconductor processing chamber; contacting a substrate housed in the substrate processing region with the water vapor and the fluorine-containing precursor, wherein the substrate defines a trench, wherein a layer of an oxygen-containing material is disposed within the trench and exposed on the substrate; halting the flow of water vapor while maintaining the flow of the fluorine-containing precursor; and removing the oxygen-containing material.
 15. The removal method of claim 14, wherein the water vapor is delivered into the substrate processing region at a temperature above or about −40° C.
 16. The removal method of claim 14, wherein the fluorine-containing precursor is flowed at a rate of less than or about 500 sccm during the removal method.
 17. The removal method of claim 14, wherein the fluorine-containing precursor is delivered in pulses, wherein the delivery is characterized by a first period of time during which the fluorine-containing precursor is flowed, and a second period of time during which the fluorine-containing precursor flow is halted.
 18. The removal method of claim 17, wherein the first period of time and the second period of time are both greater than or about 2 seconds.
 19. The removal method of claim 14, wherein the fluorine-containing precursor is anhydrous hydrogen fluoride, and wherein the substrate processing region is maintained plasma-free during the removal method.
 20. An etching method comprising: flowing a hydrogen-containing precursor into a substrate processing region of a semiconductor processing chamber while maintaining the substrate process region at a temperature between about −50° C. and about 0° C.; flowing anhydrous hydrogen fluoride into the substrate processing region; contacting a substrate housed in the substrate processing region with the hydrogen-containing precursor and the anhydrous hydrogen fluoride, wherein the substrate defines a trench, wherein a layer of an oxygen-containing material is disposed within the trench and exposed on the substrate; halting the flow of the hydrogen-containing precursor; and removing the oxygen-containing material. 